p_unix.cpp

UPX 源代码

        int l = fi->readx(ibuf, UPX_MIN(rest, (off_t)blocksize));
        if (l == 0) {
            break;
        }
        rest -= l;

        // Note: compression for a block can fail if the
        //       file is e.g. blocksize + 1 bytes long

        // compress
        ph.c_len = ph.u_len = l;
        ph.overlap_overhead = 0;
        unsigned end_u_adler = 0;
        if (ft) {
            // compressWithFilters() updates u_adler _inside_ compress();
            // that is, AFTER filtering.  We want BEFORE filtering,
            // so that decompression checks the end-to-end checksum.
            end_u_adler = upx_adler32(ibuf, ph.u_len, ph.u_adler);
            ft->buf_len = l;

                // compressWithFilters() requirements?
            ph.filter = 0;
            ph.filter_cto = 0;
            ft->id = 0;
            ft->cto = 0;

            compressWithFilters(ft, OVERHEAD, NULL_cconf, filter_strategy,
                                0, 0, 0, hdr_ibuf, hdr_u_len);
        }
        else {
            (void) compress(ibuf, ph.u_len, obuf);    // ignore return value
        }

        if (ph.c_len < ph.u_len) {
            const upx_bytep tbuf = NULL;
            if (ft == NULL || ft->id == 0) tbuf = ibuf;
            ph.overlap_overhead = OVERHEAD;
            if (!testOverlappingDecompression(obuf, tbuf, ph.overlap_overhead)) {
                // not in-place compressible
                ph.c_len = ph.u_len;
            }
        }
        if (ph.c_len >= ph.u_len) {
            // block is not compressible
            ph.c_len = ph.u_len;
            memcpy(obuf, ibuf, ph.c_len);
            // must update checksum of compressed data
            ph.c_adler = upx_adler32(ibuf, ph.u_len, ph.saved_c_adler);
        }

        // write block sizes
        b_info tmp;
        if (hdr_u_len) {
            unsigned hdr_c_len = 0;
            MemBuffer hdr_obuf;
            hdr_obuf.allocForCompression(hdr_u_len);
            int r = upx_compress(hdr_ibuf, hdr_u_len, hdr_obuf, &hdr_c_len, 0,
                ph.method, 10, NULL, NULL);
            if (r != UPX_E_OK)
                throwInternalError("header compression failed");
            if (hdr_c_len >= hdr_u_len)
                throwInternalError("header compression size increase");
            ph.saved_u_adler = upx_adler32(hdr_ibuf, hdr_u_len, init_u_adler);
            ph.saved_c_adler = upx_adler32(hdr_obuf, hdr_c_len, init_c_adler);
            ph.u_adler = upx_adler32(ibuf, ph.u_len, ph.saved_u_adler);
            ph.c_adler = upx_adler32(obuf, ph.c_len, ph.saved_c_adler);
            end_u_adler = ph.u_adler;
            memset(&tmp, 0, sizeof(tmp));
            set_native32(&tmp.sz_unc, hdr_u_len);
            set_native32(&tmp.sz_cpr, hdr_c_len);
            tmp.b_method = (unsigned char) ph.method;
            fo->write(&tmp, sizeof(tmp));
            b_len += sizeof(b_info);
            fo->write(hdr_obuf, hdr_c_len);
            total_out += hdr_c_len;
            total_in  += hdr_u_len;
            hdr_u_len = 0;  // compress hdr one time only
        }
        memset(&tmp, 0, sizeof(tmp));
        set_native32(&tmp.sz_unc, ph.u_len);
        set_native32(&tmp.sz_cpr, ph.c_len);
        if (ph.c_len < ph.u_len) {
            tmp.b_method = (unsigned char) ph.method;
            if (ft) {
                tmp.b_ftid = (unsigned char) ft->id;
                tmp.b_cto8 = ft->cto;
            }
        }
        fo->write(&tmp, sizeof(tmp));
        b_len += sizeof(b_info);

        // write compressed data
        if (ph.c_len < ph.u_len) {
            fo->write(obuf, ph.c_len);
            // Checks ph.u_adler after decompression, after unfiltering
            verifyOverlappingDecompression(ft);
        }
        else {
            fo->write(ibuf, ph.u_len);
        }

        if (ft) {
            ph.u_adler = end_u_adler;
        }
        total_in += ph.u_len;
        total_out += ph.c_len;
    }
}

void PackUnix::unpackExtent(unsigned wanted, OutputFile *fo,
    unsigned &total_in, unsigned &total_out,
    unsigned &c_adler, unsigned &u_adler,
    bool first_PF_X, unsigned szb_info
)
{
    b_info hdr; memset(&hdr, 0, sizeof(hdr));
    while (wanted) {
        fi->readx(&hdr, szb_info);
        int const sz_unc = ph.u_len = get_native32(&hdr.sz_unc);
        int const sz_cpr = ph.c_len = get_native32(&hdr.sz_cpr);
        ph.filter_cto = hdr.b_cto8;

        if (sz_unc == 0) { // must never happen while 0!=wanted
            throwCompressedDataViolation();
            break;
        }
        if (sz_unc <= 0 || sz_cpr <= 0)
            throwCompressedDataViolation();
        if (sz_cpr > sz_unc || sz_unc > (int)blocksize)
            throwCompressedDataViolation();

        int j = blocksize + OVERHEAD - sz_cpr;
        fi->readx(ibuf+j, sz_cpr);
        // update checksum of compressed data
        c_adler = upx_adler32(ibuf + j, sz_cpr, c_adler);
        // decompress
        if (sz_cpr < sz_unc)
        {
            decompress(ibuf+j, ibuf, false);
            if (12==szb_info) { // modern per-block filter
                if (hdr.b_ftid) {
                    Filter ft(ph.level);  // FIXME: ph.level for b_info?
                    ft.init(hdr.b_ftid, 0);
                    ft.cto = hdr.b_cto8;
                    ft.unfilter(ibuf, sz_unc);
                }
            }
            else { // ancient per-file filter
                if (first_PF_X) { // Elf32_Ehdr is never filtered
                    first_PF_X = false;  // but everything else might be
                }
                else if (ph.filter) {
                    Filter ft(ph.level);
                    ft.init(ph.filter, 0);
                    ft.cto = (unsigned char) ph.filter_cto;
                    ft.unfilter(ibuf, sz_unc);
                }
            }
            j = 0;
        }
        // update checksum of uncompressed data
        u_adler = upx_adler32(ibuf + j, sz_unc, u_adler);
        total_in  += sz_cpr;
        total_out += sz_unc;
        // write block
        if (fo)
            fo->write(ibuf + j, sz_unc);
        wanted -= sz_unc;
    }
}

/*************************************************************************
// Generic Unix canUnpack().
**************************************************************************/

int PackUnix::canUnpack()
{
    upx_byte buf[128];
    const int bufsize = sizeof(buf);

    fi->seek(-bufsize, SEEK_END);
    fi->readx(buf, bufsize);
    if (!getPackHeader(buf, bufsize, true))  // allow incompressible extents
        return false;

    int l = ph.buf_offset + ph.getPackHeaderSize();
    if (l < 0 || l + 4 > bufsize)
        throwCantUnpack("file corrupted");
    overlay_offset = get_native32(buf+l);
    if ((off_t)overlay_offset >= file_size)
        throwCantUnpack("file corrupted");

    return true;
}


/*************************************************************************
// Generic Unix unpack().
//
// This code looks much like the one in stub/l_linux.c
// See notes there.
**************************************************************************/

void PackUnix::unpack(OutputFile *fo)
{
    unsigned szb_info = sizeof(b_info);
    {
        Elf32_Ehdr ehdr;
        fi->seek(0, SEEK_SET);
        fi->readx(&ehdr, sizeof(ehdr));
        unsigned const e_entry = get_native32(&ehdr.e_entry);
        if (e_entry < 0x401180) { /* old style, 8-byte b_info */
            szb_info = 2*sizeof(unsigned);
        }
        else {
            Elf32_Phdr phdr;
            fi->seek(get_native32(&ehdr.e_phoff), SEEK_SET);
            fi->readx(&phdr, sizeof(phdr));
            unsigned const p_vaddr = get_native32(&phdr.p_vaddr);
            if (0x80==(e_entry - p_vaddr)) { /* 1.22 old style */
                szb_info = 2*sizeof(unsigned);
            }
        }
    }

    unsigned c_adler = upx_adler32(NULL, 0);
    unsigned u_adler = upx_adler32(NULL, 0);

    // defaults for ph.version == 8
    unsigned orig_file_size = 0;
    blocksize = 512 * 1024;

    fi->seek(overlay_offset, SEEK_SET);
    if (ph.version > 8)
    {
        p_info hbuf;
        fi->readx(&hbuf, sizeof(hbuf));
        orig_file_size = get_native32(&hbuf.p_filesize);
        blocksize = get_native32(&hbuf.p_blocksize);

        if (file_size > (off_t)orig_file_size || blocksize > orig_file_size)
            throwCantUnpack("file header corrupted");
    }
    else
    {
        // skip 4 bytes (program id)
        fi->seek(4, SEEK_CUR);
    }

    ibuf.alloc(blocksize + OVERHEAD);

    // decompress blocks
    unsigned total_in = 0;
    unsigned total_out = 0;
    b_info bhdr; memset(&bhdr, 0, sizeof(bhdr));
    for (;;)
    {
#define buf ibuf
        int i;
        unsigned sz_unc, sz_cpr;

        fi->readx(&bhdr, szb_info);
        ph.u_len = sz_unc = get_native32(&bhdr.sz_unc);
        ph.c_len = sz_cpr = get_native32(&bhdr.sz_cpr);

        if (sz_unc == 0)                   // uncompressed size 0 -> EOF
        {
            // note: must reload sz_cpr as magic is always stored le32
            sz_cpr = get_le32(&bhdr.sz_cpr);
            if (sz_cpr != UPX_MAGIC_LE32)  // sz_cpr must be h->magic
                throwCompressedDataViolation();
            break;
        }
        if (sz_unc <= 0 || sz_cpr <= 0)
            throwCompressedDataViolation();
        if (sz_cpr > sz_unc || sz_unc > blocksize)
            throwCompressedDataViolation();

        i = blocksize + OVERHEAD - sz_cpr;
        fi->readx(buf+i, sz_cpr);
        // update checksum of compressed data
        c_adler = upx_adler32(buf + i, sz_cpr, c_adler);
        // decompress
        if (sz_cpr < sz_unc) {
            decompress(buf+i, buf, false);
            if (0!=bhdr.b_ftid) {
                Filter ft(ph.level);
                ft.init(bhdr.b_ftid);
                ft.cto = bhdr.b_cto8;
                ft.unfilter(buf, sz_unc);
            }
            i = 0;
        }
        // update checksum of uncompressed data
        u_adler = upx_adler32(buf + i, sz_unc, u_adler);
        total_in  += sz_cpr;
        total_out += sz_unc;
        // write block
        if (fo)
            fo->write(buf + i, sz_unc);
#undef buf
    }

    // update header with totals
    ph.c_len = total_in;
    ph.u_len = total_out;

    // all bytes must be written
    if (ph.version > 8 && total_out != orig_file_size)
        throwEOFException();

    // finally test the checksums
    if (ph.c_adler != c_adler || ph.u_adler != u_adler)
        throwChecksumError();
}


/*
vi:ts=4:et
*/